<!DOCTYPE html>
<html>
 
<head>
    <style>
        .wrap {
            width: 800px;
            height: 400px;
            position: relative;
        }
 
        .list {
            width: 800px;
            height: 400px;
            position: relative;
            padding-left: 0px;
        }
 
        .item {
            width: 100%;
            height: 100%;
            list-style: none;
            position: absolute;
            left: 0;
            opacity: 0;
            transition: all .8s;
            border: 1px solid red;
        }
 
        .item:nth-child(1) {
            background-color: skyblue;
        }
 
        .item:nth-child(2) {
            background-color: yellowgreen;
        }
 
        .item:nth-child(3) {
            background-color: rebeccapurple;
        }
 
        .item:nth-child(4) {
            background-color: pink;
        }
 
        .item:nth-child(5) {
            background-color: orange;
        }
 
        .item.active {
            z-index: 10;
            opacity: 1;
        }
 
        .btn {
            width: 60px;
            height: 100px;
            z-index: 100;
            top: 150px;
            position: absolute;
        }
 
        #leftBtn {
            left: 0px;
        }
 
        #rightBtn {
            right: 0px;
        }
 
        .pointList {
            list-style: none;
            padding-left: 0px;
            position: absolute;
            right: 20px;
            bottom: 20px;
            z-index: 200;
        }
 
        .point {
            width: 10px;
            height: 10px;
            background-color: antiquewhite;
            border-radius: 100%;
            float: left;
            margin-right: 8px;
            border-style: solid;
            border-width: 2px;
            border-color: slategray;
            cursor: pointer;  
        }
 
        .point.active{
            background-color: cadetblue;
        }
    </style>
</head>
 
<body>
    <div class="wrap">
        <ul class="list">
          <li class="item active">
              <img src="./images/lunbo_01.png">
          </li>
          <li class="item active">
              <img src="./images/banner@3x.jpg">
          </li>
          <li class="item active">
              <img src="./images/lunbo_01.png">
          </li>
          <li class="item active">
            <img src="./images/banner@3x.jpg">
          </li>
          <li class="item active">
            <img src="./images/lunbo_01.png">
          </li>
        </ul>
        <ul class="pointList">
            <li class="point active" data-index = 0></li>
            <li class="point" data-index = 1></li>
            <li class="point" data-index = 2></li>
            <li class="point" data-index = 3></li>
            <li class="point" data-index = 4></li>
        </ul>
        <button class="btn" id="leftBtn"> < </button> 
        <button class="btn" id="rightBtn"> > </button>
 
    </div>
    <script>
        var items = document.querySelectorAll(".item");//图片
        var points = document.querySelectorAll(".point")//点
        var left = document.getElementById("leftBtn");
        var right = document.getElementById("rightBtn");
        var all = document.querySelector(".wrap")
        var index = 0;
        var time = 0;//定时器跳转参数初始化
        
 
        //清除active方法
        var clearActive = function () {
            for (i = 0; i < items.length; i++) {
                items[i].className = 'item';
            }
            for (j = 0; j < points.length; j++) {
                points[j].className = 'point';
            }
        }
 
        //改变active方法
        var goIndex = function () {
            clearActive();
            items[index].className = 'item active';
            points[index].className = 'point active'
        }
        //左按钮事件
        var goLeft = function () {
            if (index == 0) {
                index = 4;
            } else {
                index--;
            }
            goIndex();
        }
 
        //右按钮事件
        var goRight = function () {
            if (index < 4) {
                index++;
            } else {
                index = 0;
            }
            goIndex();
        }
        
 
        //绑定点击事件监听
        left.addEventListener('click', function () {
            goLeft();
            time = 0;//计时器跳转清零
        })
 
        right.addEventListener('click', function () {
            goRight();
            time = 0;//计时器跳转清零
        })
 
        for(i = 0;i < points.length;i++){
            points[i].addEventListener('click',function(){
                var pointIndex = this.getAttribute('data-index')
                index = pointIndex;
                goIndex();
                time = 0;//计时器跳转清零
            })
        }
        //计时器
        var timer;
        function play(){
         timer = setInterval(() => {
            time ++;
            if(time == 20 ){
                goRight();
                time = 0;
            }    
        },100)
    }
        play();
        //移入清除计时器
        all.onmousemove = function(){
            clearInterval(timer)
        }
       //移出启动计时器
        all.onmouseleave = function(){
            play();
        }
    </script>
</body>
 
</html>